Random Access Versus Multiple Access

Gaudenzi, R. De; Herrero, Oscar del Río; Cioni, Stefano; Mengali, Alberto

doi:10.1007/978-3-319-92090-0_17

Cited by 4 publications

(7 citation statements)

References 54 publications

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“…Spreading-based multiple access is adopted for individual low-power consumption and to cope with low peak-to-average-power ratios, at the cost of increasing the users' transmission time. For these reasons and complying with previous works [26]- [28], users sign packets leveraging spreading codes with period much higher than the symbol interval 2 . c k,m (t) is the spreading waveform of user k for symbol m, which has an average per-symbol cross-correlation gain proportional to the inverse of the spreading factor N [14].…”

Section: System Modelsupporting

confidence: 53%

“…When the number of users is sufficiently large over the coverage area and its ordered profile h of channel power gains is known, we can design an allocation function g(h) based on 1 The multipath components in a channel dominated by strong line-ofsight contribute to increasing the system noise level after symbol despreading as the receiver only processes the line-of-sight component for each user. 2 to have Gaussian distributed interference at the despreader's output.…”

Section: System Modelmentioning

confidence: 99%

“…An explosive growth of smart devices enabling short packet transmissions is expected. Hence, the main target nowadays is the analysis of multiple access schemes that can support such a high number of possibly small and powerefficient devices, distributed either over a large area or more densely over a smaller area, and that transmit infrequently whenever they are ready or on a periodic scheduled basis if, for example, they track some continuous parameter [2].…”

Section: Introductionmentioning

confidence: 99%

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Energy Allocation Design for the Satellite Return Channel of a Massive NOMA System With Interference Cancellation

Molina

Sala-Alvarez

2022

IEEE Trans. on Green Commun. Netw.

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The energy allocation problem in a massive access setting under iterative successive interference cancellation (SIC) is undertaken in this work. The classic one-iteration SIC still has room for improvement when the channel coding schemes adopted are non-error free. In this work, we investigate a satellite return link in which transmitters employ the same physical layer and transmission protocol: a given encoder, and spreading-based nonorthogonal multiple access. Leveraging iterative SIC, the gateway is endowed with strong interference suppression potential to deal with many uncoordinated transmissions. We elaborate on the interplay between energy and reliability for all users by designing an energy allocation with minimum energy expenditure when the iterative SIC receiver performs two decoding attempts per user. We resort to the user-asymptotic regime to address the randomness in the multi-feature system model of two-iteration SIC, which has turned the analysis into a deterministic one. We formulate our final design as a vector optimization aided by tools from the calculus of variations. We show the competitive performance achieved by the designed allocation, specially under encoders associated with short-length codes. We also assess our analysis by simulating a low-level SIC implementation.

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Section: System Modelsupporting

confidence: 53%

Section: System Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Energy Allocation Design for the Satellite Return Channel of a Massive NOMA System With Interference Cancellation

Molina

Sala-Alvarez

2022

IEEE Trans. on Green Commun. Netw.

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“…The asymptotic large-user assumption provides a very comfortable result in that N t (t) in ( 16), the denominator of Γ(t), turns out to be deterministic rather than the sum of random variables in (12). The relevant finding is that the SIC receiver can be seen as a dynamical system, whose behavior can be characterized through deterministic expressions either in differential or integral form.…”

Section: ) Concluding Remarksmentioning

confidence: 99%

“…The successful idea has been to enable nonorthogonal multiple access (NOMA) and adopt a multiuser receiver to resolve destructive packet collisions. This scheme enables the autonomous operation of multiple devices in exchange for increasing the complexity of the receiver, which must adopt an algorithm for detecting many users [11], [12]. Such is the case for the slotted [13] or the asynchronous [14] versions of the contention resolution diversity ALOHA protocol, which transmit many copies of the same packet and rely on an interference cancellation (IC) based demodulator.…”

Section: Introductionmentioning

confidence: 99%

Energy and Rate Allocation for Massive Multiple Access With Interference Cancelation

et al. 2022

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This article addresses the problem of energy and code allocation to many users accessing, under spreading-based nonorthogonal multiple access, a wireless node set up with a successive interference cancellation architecture aided by redundancy-check error control. As an application, we consider the asynchronous access of a delay-tolerant satellite system, where users employ finite-length channel codes and are subject to a known power unbalance induced by the known distribution of the channel's attenuation. The article develops, as a mathematically tractable approximation to massively populated systems, a unified framework to compute the best energy and code allocation rules that maximize the spectral efficiency of a network that handles asymptotically many users. Concretely, the presented approach circumvents the exponential complexity in the number of users when modeling the propagation of packet decoding failures through the receiver's decoding scheme. It also enables a deterministic analysis of the more complex features affecting the receiver, making the related performance optimization problem amenable to systematic tools from differential and variational calculus. The derived expressions evidence the most favorable three-way unbalance between energy, rate, and reliability for receiver performance. Low-level system simulations are carried out for validation.INDEX TERMS Massive multiple access, successive interference cancellation, satellite, energy and code allocation, asymptotic analysis.

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